Various fluoropolymers have been proposed for imparting oil and water repellency to leather. Commonly, these fluoropolymers are amphiphilic; i.e., they are made from at least one monomer which is hydrophobic and at least one monomer which is hydrophilic. The present invention identifies and remedies disadvantages associated with the ability of amphiphilic fluoropolymers to impart oil and water repellency to leather.
Proposals of amphiphilic fluoropolymers for imparting oil and water repellency are summarized herein and include U.S. Pat. No. 5,316,860 which discloses amphiphilic copolymers for improving the strength, temper, and water resistance of the leather. The amphiphilic copolymers are formed from a predominant amount of at least one hydrophobic monomer and a minor amount of at least one copolymerizable hydrophilic monomer. U.S. Pat. No. 5,534,604 discloses copolymers comprising ethylenically unsaturated dicarboxylic acid anhydrides, long chain olefins and fluoroolefin. U.S. Pat. No. 5,124,181 discloses copolymers polymerized from (a) alkyl methacrylates, vinyl esters of carboxylic acids or mixtures thereof and (b) monoethylenically unsaturated carboxylic acids, monoethylenically unsaturated dicarboxylic anhydrides, monoesters or monoamides of monoethylenically unsaturated dicarboxylic acids, amides of monocarboxylic acids. U.S. Pat. No. 5,741,434 discloses water-dispersible and/or water-emulsifiable co-oligomers containing (a) fatty crotonates; (b) radically copolymerizable, hydrophilic, ethylenically unsaturated acids and/or their anhydrides; and possibly (c) minor amounts of other copolymerizable comonomers.
Use of the aforementioned amphiphilic copolymers appears to be predicated on the belief that the hydrophilic portion (typically a carboxylic acid group) of these copolymers is necessary for imparting water resistance to leather. An expression of this conventional thinking may be found in U.S. Pat. No. 6,294,103 which advises: “if the carboxylic acid content is low the copolymer may not adequately penetrate the leather structure and/or may not bind sufficiently into the leather.”